TypeScript Node.js testing tips

Situation 1

Use mocha in server-side TypeScript projects with compilerOptions.paths in tsconfig.json ?

Then we need:

1. mocha
2. tsconfig-paths
3. ts-node
4. { "ts-node": { "files": true } } in the tsconfig.json file (see more here)

Depending on how we import our modules around in the codebase, point (4) above may not always be needed. In one of my projects, it was crucial.

Then run our test with e.g:

mocha --require ts-node/register --require tsconfig-paths/register

So that compilerOptions.paths in our tsconfig.json file is respected.

This way we can test directly against our .ts files

Situation 2

Use jest in server-side TypeScript projects?

• add { "testEnvironment": "node" } to the config (e.g. the jest entry in package.json or equivalents)
• <rootDir> token can be used inside moduleDirectories
• moduleNameMapper can be useful